UN 2501 — Tris-(1-aziridinyl)phosphine oxide, solution
Placard: Toxic. ERG Guide 152. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2501 is Tris-(1-aziridinyl)phosphine oxide, solution, a highly toxic solution assigned to ERG Guide 152. Exact concentration/solvent must be verified from SDS.
Hazard overview: HIGHLY TOXIC aziridine/phosphoramide solution; inhalation, ingestion or skin absorption may be fatal. Skin contact and contaminated clothing can extend exposure. Combustible material: may burn but does not ignite readily.
Response guidance: For UN 2501, isolate the area, avoid skin contact and use SCBA where vapor, dust, mist or fire is present. Contain toxic/corrosive runoff and verify product controls with SDS and ERG 152.
Firefighter training notes: Training for UN 2501 should emphasize toxic/corrosive exposure routes, skin absorption, SCBA use, decontamination, runoff containment and SDS verification. Use ERG 152, SDS and local SOP.
Regulatory context: Tris-(1-aziridinyl)phosphine oxide, solution is regulated as a hazardous material for transport and emergency response. Storage, exposure, spill reporting, waste and fire-code duties depend on quantity, concentration and jurisdiction; verify shipping papers, SDS and local authority requirements.
Storage & handling: Tris-(1-aziridinyl)phosphine oxide, solution should be stored in tightly closed compatible containers with ventilation, secondary containment, restricted access and SDS-based segregation from incompatible materials.
UN 2501 Quick Details
Common Hazards of UN 2501
- HIGHLY TOXIC aziridine/phosphoramide solution; inhalation, ingestion or skin absorption may be fatal.
- Skin contact and contaminated clothing can extend exposure.
- Combustible material: may burn but does not ignite readily.
- May be reactive or unstable under heat or contamination depending on solution composition.
- Fire may produce nitrogen oxides, phosphorus oxides and other toxic gases.
- Runoff may carry toxic solution contamination.
- Exact solvent/concentration must be verified from SDS and shipping papers.
Chemical Identity & Physical Properties
Colorless to pale yellow liquid solution. Odorless or slight amine-like odor. Highly toxic organic compound used historically as a chemotherapy agent and insect chemosterilant.
| Also known as | TEPATris(1-aziridinyl)phosphine oxideTriethylenephosphoramideAPOTris(ethylenimino)phosphine oxide |
| CAS Number | 545-55-1 |
| Appearance | Colorless to pale yellow liquid solution. Odorless or slight amine-like odor. Highly toxic organic compound used historically as a chemotherapy agent and insect chemosterilant. |
| Flash Point | Not available for solution; base compound is combustible |
| Boiling Point | Decomposes before boiling at approximately 80-100°C (176-212°F) |
| Vapor Density | Heavier than air (MW ~173) |
| Water Reactivity | Soluble in water; no violent reaction but releases toxic vapors |
Fireground Response Guidance — UN 2501
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for vapor, dust, mist, fire or confined-space exposure. Wear chemical-resistant gloves, boots, eye/face protection and protective clothing.
Isolation & Evacuation
First Actions for a UN 2501 Incident
- Call 911 and the emergency response number on the shipping paper, if available.
- Keep unauthorized personnel away and establish incident command.
- Stay upwind, uphill and upstream.
- Avoid breathing vapor, dust, mist, smoke or fumes and avoid skin or eye contact.
- Do not touch damaged containers or spilled material without proper training and PPE.
- Prevent contaminated dust, liquid, runoff and decontamination waste from spreading.
- Ventilate confined spaces only after monitoring and only if properly trained and equipped.
- Use ERG Guide 152, SDS, shipping papers and monitoring to set isolation, evacuation and entry decisions.
📋 Copy & Share Field Card
UN 2501 — Tris-(1-aziridinyl)phosphine oxide, soluUse for: Quick radio or face-to-face size-up. Short, structured, field-ready.
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
Use for: Quick text to command or incoming units. Fits in a single SMS.